Extraction of krypton and xenon from air



May 15, 1928. I r

A. J. A. BLARINGHEM EXTRACTION OF KRYPT ON AND XENON FROM AIR Filed May 26, 1924 fl-J 4. Waring/19m mven tar Patented May 15 1928. v

UNITED STATES 1,670,014 PATENT OFFICE.

AUGUSTE JULES ADRIEN BLARINGHEM, OF MAZINGARBE, FRANCE, ASSIGNOR '10 SOGIETE ANONYME DECLAIRAGE ET DAIPPLIGATIONS ELECTBIQUES, OF AREAS,

PASp-DE-OALAIS, FRANCE.

nx'rnaorron or KRYPTON AND XENON 30m AIR.

Application filed May 26, 1924, Serial No. 216,065, and in France June 29, 1923.

This invention relates-to processes of recovering krypton and xenon, from liquid oxygen containing the same and it comprises a. process in which liquefied oxygen is al- 5 lowed to evaporate and the vapors thereof passed'through an absorbent material such as carbon; it further comprises a process in which the absorbent material is kept cold by means of gaseous oxygen.

Notwithstanding their relatively high boiling points (respectively l51.8 and 106.9) ,krypton and xenon have an appreciable volatility at the temperature of liquid air. This is the chief reason why they can v not be obtained as a'residue from the evaporation of liquid oxygen. I

Thus, after a prolonged operation of an industrial oxygen liquefying apparatus, only a small fraction of the amount of krypton and xenon which have passed through the apparatus is obtained in the residue from the'evaporation of the liquid oxygen.

The experiments made by the applicant have shown, in fact, that these gases, krypton and xenon, progressively acc unulated in the liquid oxygen in an apparatus working in a prolonged and continuous manner (as is the case of actual industrial apparatus) soon acquire therein an appreciable vapour tension, considering the small quantities present, and gradually increasing in proportion to the admission of the gases. 'A progressively increasing 'quantity of these gases, will there fore escape with the oxygen, until there willbe an equilibrium established betw en the quantities which enter and those which escape. p Enlightened by these considerations, instead of recovering krypton and xenon from the residue of liquid oxygen, the present inventor essentially employs for the extraction. of krypton and xenon, gaseous oxygen supplied in the course of operation of the apparatus.

This method has first the capital advan tage that the individual oxygen apparatus can thus be used for the extraction of the said gases, without being modified in their princlple, or changed in their operation.

The annexed drawing shows, by way of example, the application of the process in an apparatus of the type Claude for the production of oxygen by the liquefaction of air. In this apparatus, a is the reservoir, 6 are the cylinders .of the aircompressor, v(Lathe pipe line of the refrigerator ot the compressor, (1 the exchanger, 6 the expansion cylinder, 7 the entrance of the compressed oxygen at critical temperature, 9 the exchanger for the liquid oxygen; Z is aliquid oxygen reservoir;

The reservoir, containing the absorbing material is disposed at the outlet of the liquefier, It is traversed by the current of the gaseousoxygen; n is the pipe line which permits extraction of the krypton and the xenon retained by the absorbing material.

Suitable valves-arc associated with the pipes in order to control the system. This extraction operates naturally after the circulation of the gaseous oxygen in the reservoir is interrupted. I

The process is based on the fact that if this oxygen is passed over or through carbon, or similar materials, silica for instance at an intermediate temperature between -l82.5 and the surrounding temperature, this carbon, which will be very rapidly saturated with oxygen, will first of all in addition retain krypton and xenon under tensions much lower than their normal tensions at the same temperature. tension will gradually increase and the accumulation of these gases will not be capable Here again, the

understood that this limit will depend to a considerable extent on the temperature.

Even if the operation is carried out at a temperature in the neighbourhood of -182.5, the tensions of krypton and xenon can'remain indefinitely small and, with a suflicient mass of carbon, the saturation will be reached or even approached only after a very long time, which can exceed the longest practical periods of operation of industrial apparatus.

A large portion of krypton and xenon of the'air treated can thus be retained and extracted bythe fine carbon.

The principle of the method consists therefore in causing the oxygen produced by the oxygen apparatus to pass into a vessel containing a suflicient quantity of carbon or another suitable material and maintained at a suitable temperature so that the equilibrium in krypton and xenon is not reached or even, if possible, approached during the period of operation of the apparatus.

Another feature of thepresent'invention consistsin the manner of maintaining the carbon at thelow temperature most suitable. The means forming the subject-matter of this phase of the invention consists in giving heat exchangers mounted in series, the

oxygen will issue from the coldest of these heat exchangers for entering in the other at a temperature so much the more lower as the exchange surface of the first will be smaller relatively to that of the second, this temperature can therefore be chosen at will by a suitable choice of the exchange surface. By interposing the carbon vessel in the path of the oxygen between the heat exchangers, the carbon will thus be subjected to the desired temperature. As there is no inconvenience, but actually advantages, in operating at a very low te1nperature, it is thus possible to dispense with a special heat exchanger in oxygen apparatus which, as in those of Claude, comprise a liquefying device where this oxygen begins to heat up. The oxygen will then be directly admitted in the carbon vessel as it issues from the liquefying device. It can be even allowed to come in contact with carbon when issuing from the vaporizer.

Thus nothing will be changed in oxygen apparatus, besides the adjunction of the caraemou bon vessel which can be arranged, if desired,

in the heat preservin mass of the a paratus.

Of course, and t 's is particu arly interesting in the case of operations of short duration, it is advantageous not to neglect the liquid residue from the evaporation of the oxygen, which remains in the oxygen apparatus at the-end of the operation and which necessarily contains relatively large quantities of krypton and particularly of xenon. For that purpose, the residue may, if necessary, be vaporized in a special vessel and the products of vaporization directed in a carbon vessel answering to the above conditions.

to secure by Letters Patent is:

1. The process of extracting kry ton and xenon from liquefied oxygen containing the same which comprises evaporating said liquefied oxygen and passing the vapors formed by the evaporation into contact with gasabsorbing substances;

2. In the process of claim 1, the step which comprises maintaining the absorbing substances at a low temperature by means of a cold stream of ga'seous-oxygenproduced in the process.

3. The process of extracting kry ton and xenon from liquefied oxygen containing the same which comprises evaporating said lVhat I claim as my invention and desire.

liquefied oxygen, passing the vapors formed by theeva oration into contact with as absorbing s11 stances and recovering urther quantities of'krypton and xenon from the residue from the evaporation of the liquefied oxygen.

In testimony -whereof I have signed my name to this specification.

AUGUSTE JULES ADRIEN BLARINGHEM. 

